SpeculativeExecution: fix incorrect debug info move

Summary:
Debug info related instructions got zero cost so hoisted unconditionally

Bugzilla: https://bugs.llvm.org/show_bug.cgi?id=46267

Reviewers: arsenm, nhaehnle, chandlerc, aprantl

Reviewed By: aprantl

Subscribers: ormris, uabelho, wdng, aprantl, hiraditya, llvm-commits

Tags: #llvm, #debug-info

Differential Revision: https://reviews.llvm.org/D81730